A general food container cover includes front, back, and side locking wings with respective living hinges. As to such a cover, the locking wings are engaged with protrusions on the outer surface of the body of a food container so that the cover is fixed to the body of the food container. There is a different type of food container cover. This type includes a viewing cover and a frame member with locking wings. This cover is fixed to the body of a food container in a manner that the viewing cover is first combined with the frame member having the locking wings, and then the locking wings are engaged with protrusions formed on the outer surface of the body of the food container.
The cover having the structure in which the cover body and the locking wings are integrally formed is formed of a flexible synthetic resin. The cover having the structure in which the frame member and the viewing cover are separately provided and combined for use has advantages: the viewing cover formed of a transparent material allows the user to view the inside of a food container without opening a cover; and the viewing cover and the frame member are allowed to differ in color so that the cover may have two colors, which may impart the cover with an attractive appearance.
On the other hand, “an air tight container comprising double covers” which was applied for a utility model by the present applicant of this application and is now registered as a utility model under a utility model registration number of 033117, includes a typical container body and a special cover that closes the container body. In the technology, either the container body or the cover is provided with locking wings, and the other is provided with fixing protrusions to be engaged with the locking wings. The cover includes: a flexible coupling cover including a frame-shaped body, an accommodating portion which is the same in shape to the opening of the container body and accommodates the edge of the opening of the container body therein when the cover closes the opening of the container body, and an opening at the center thereof; and a viewing cover including a plate-like lid arranged at the position of the opening of the viewing cover, and a combining unit which extends outward from the edge of the lid, curves downward, is to be accommodated in the accommodating portion of the coupling cover, and has a plurality of combining protrusions protruding upward from the top surface thereof at predetermined intervals. The coupling cover has a plurality of combining holes in the accommodating portion at the positions corresponding to the combining protrusions so that the combining protrusions of the combining unit pass through the accommodating portion and are inserted into the combining holes. The combining unit has a channel-shaped combining slot open at the bottom of the combining unit so that the edge of the opening of the container body can be fitted into the slot. The combining unit with the combining slot of the viewing cover is received in the accommodating portion of the coupling cover so that the viewing cover and the coupling cover are combined.
However, the cover of the airtight container with double covers brings the disadvantages that it is difficult to manufacture the cover due to its complicated structure, and a frame member is highly likely to be separated from the viewing cover by even a very weak physical force because the combining unit of the viewing cover is inserted in the accommodating portion of the coupling cover.